Formation sealing composition



Aug. 27, 1940. v. w. DAVID FoRMATIoNsEALIm-r coMPosrTroN Filed Jung 27, 193s ATTORNEY atented ug. i940' i i 12 Claims.

The present invention relates to a water shutolf sealing composition. This sealing composition, while adaptable for many purposes, nevertheless has been particularly compounded with 5 the idea of using the same as a substitute for cement in the shutting off of water from water sands, such as are sometimes encountered in an oil Well.

Most States have a law to the effect that any water tending to seep within a well hole must be shut off in some manner. The general practice is to utilize cement which is pumped through a tubing, and which cement travels outside the casing for the purpose of sealing oi the waterbearing sands, as well as sealing olf sands which contain both water and oil. i

The inventor is aware of the fact that certain operators have attempted to seal oi water bearing sands by the use of rotary mud. However, it is common knowledge that said mud is not satisfactory in that it only in some cases provides a temporary seal and does not in any case result in a permanent seal.

An object of the present invention is to utilize a composition having qualities which render it impervious to water, and which composition may be readily run through a pump tubing under pressure, to in `turn penetrate the water bearing sands and to permanently seal said sands so that Water will not seep within the well hole.l

Other objects are the provision of a composition which is inexpensive in cost of manufacture, not subject to deterioration, the ingredients of which may be mixed on the job, and does not require the use of skilled labor for said mixing or pumping within the well hole.

In the practice of my invention, I may utilize a mud which, in the present instance, constitutes a clay, such as the well known Mojave or Frazier 40 types. Such a mud, when brought to a given consistency, as hereinafter detailed, is adapted -to have added thereto what I term chemicals. These chemicals, together with the clay or mud, so alter the general character of the clay or mud as to cause the same to form what I term a water shut-cfr composition, the characteristic of which is a water impermeable mass both prior to its introduction within the well hole through the medium of tubing, and likewise after it is within the well hole and allowed to set. lAfter the composition has set, it becomes a hard shale.

For the purpose oi the invention, I have .detailed specically the viscosity of the clay of the Frazier or Mojave type, which are best adapted for the se of the invention, in combination.

(ci. 10c-2s) f with the chemicals which are to be added thereto. I have also indicated the pressures which are to be utilized in pumping the composition into the well hole.

It is a well known fact that as oil is depleted from oil sands, the more readily will the sand take water due to the fact that the water has a greater surface tension than the oil. Sometimes the water, once admitted to the depleted oil sands, will hang tenaciously in the pores of the sand, thus retarding flow of oil to the well. Furthermore, the chilling effect of the water on oils of the paraiiin base type may cause a formation of wax in the sand adjacent the well and. further retard production.

Another object of the invention is the provision of a suitable composition which may be utilized when circulation is lost during rotary drilling operation and for the` purpose of reestablishing circulation.

With respect to the foregoing object, it is well known4 that during'a drilling operation utilizing a rotary mud, that ofttimes the mud will strike a strata of water bearing sands, or other strata, to the end that the mud penetrates such sands or strata and the usual circulation, which is through the drill tubing and back between the casing or well hole and said tubing, is lost. When this occurs. it becomes necessary to in somel manner reestablish circulation. Various means may be resorted to, such as cementing, but this requires a great deal of workand is not at all times positive. With the present `invention, the composition may be used and allowed to remain in the well hole so that it may harden, all as hereinafter detailed. Thus, by sealing up, as it were, the sands or strata that cause the loss in the circulation, circulation is reestablished.

In the drawing:

Figure 1 illustrates a well hole having a liner passed through both oil and water sands, the water sand of which is to be shutoff or sealed, and,

Figure 2 is a longitudinal sectional view illustratin'g. means whereby the composition may be pumped through the liner and around the casing to effect water shut-off in water sands Without in any manner impairing passage of oil through the liner.

For the purpose of illustrating the use of the present composition, I have illustrated on the drawing two iigures; Figure 1, briefly described, is intended to represent a well hole surrounded by-water bearing sands, and which sands must be sealed. Figure 2 illustrates the same well hole as Figure 1, with the composition being pumped therein for the purpose of sealing the sands. In both gures, l is the well hole, 2 the well casing, and 3 a liner. As is usual practice, the lineris held to the casing by an adapter 4. A tubing 5 carries at one end a packer S, the packer of which is received in part within the adapter 4. At the surface of the well hole, a suitable cement pump may be provided so that the composition of the present invention may be forced through the tubing and packer under high pressure, to-wit, 750 to 1,000 pounds per square inch, and in turn passed outwardly through the liner so that the composition will now between the well hole and the casing and gradually ll the water sands and those sands which contain both water and cil. For instance, in both of the gures of the drawing, I have shown water sands, oil sands and oil and water sands, and it will be noted upon .viewing Figure 2 of the drawing that as to the oil sand, the composition will not set at all; in the oil and water sand, the composition will in part set, and in the water sands, the sands are completely sealed.

In carrying out my invention, utilize a clay of some type, preferably a clay having the characteristics of Frazier Mountain or Mojave. Mojave and Frazier Mountain clays are clays that are obtained from regions bearing these names in the State of California. These clays are characterized in that they have rapid dispersion in a liquid and are free of abrasive material. These clays also remain in a colloidal state in a liquid without settling out to any appreciable extent. The clay must be thoroughly mixed'with water by means cf proper instrumentalities, to the end that it has a uniform consistency and a funnel viscosity in the range of 1,000 to 10,000 seconds for 500 cc. in and 500 cc. out. The clay consistency when so mixed is that of a jelly, and the Stormer viscosity is in excess of 75 centipoises.

To this clay having the aforesaid viscosity, I add what I term my chemicals and thoroughly admix the same, such as by circulating the mix in a tank. 'I'he chemicals added have the followlng composition:

Ingredient: Per cent SiO: 18.2 FecOw 1.5 A1201 6.5 CaO 49.9 MgO 1.3 PbO 1.3 N220--- 0.3 C1-- 18.6 S03 l 0.6 Loss on ignition 1.8

The chemical mix should have a speciiic gravity between 2.1 and 2.45 and the variation in pounds per cubic foot in a dry loose state ranges between 131 and 153. When the chemicals are admixed with dry Frazier Mountain clay, the

aeiaoae 1.99 and 2.31, and the weight in pounds per cubic foot varies between 125.8 and 145.8. The permeability of the complete formula after dehydration is 3 milli-darcys, and the porosity 2.5%; in other words, the dehydrated sample is practically impermeable. In fact, when a fresh mix is made constituting the Frazier Mountain clay, plus the chemicals which are added thereto, and this fresh mix is tested in the conventional iilter-cake apparatus, under a pressure of 100 pounds per square inch, only a few drops of water are exhausted from the material in over an hours time, thus indicating that the composition is practically impermeable to commence Parts by weight Clay 100- 2li-hour cement 10.5 Calcium chloride 1l Unslaked lime 8- Prepared bentonite (para-gel) 8 Litharge .5 Flake caustic .05

Having made up the material in a fresh state at the well, this composition is forced through the tubing under the pressures named. In accordance with well known physical laws, the extent to which the composition will deposit on Athe rock walls will depend upon its colloidal state,

its rate of flow, the pressure used, and condition of the walls of the well hole. Furthermore, as

the hydrostatic head at any depth increases di' rectly with the specific gravity of the fluid, I pump the composition through the tubing under the high pressures named, for the reason, as previously stated, that the extent of penetration of the composition into the water sands varies with the porosity of the rock or sand and the excess of pressure applied.

The ingredients of my particular composition have certain physical characteristics which render my composition a superior one for the purpose of sealing water sands.

The clay, either Frazier Mountain or Mojave, or such clays as may be found, dependent upon the district, should be highly colloidal. Of

^ course, the Frazier Mountain and Mojave clays are colloidal and have a swelling action of two (2) to three (3) times their volume, when wet. Bentonite is highly colloidal, having a swelling action of six (6) to eight (8) times its volume when wetted. Bentonite also slows up the reac tion of the other ingredients in the formula, but its mostimportant function is to make the iinished mass impermeable.

The caustic lowers the surface tension of the solution, thus increasing the penetrating power 0f the mix into the formation, and aiding dispersion of the clay.

The lead oxide (litharge) acts as a negative catalyst, aiding in slowing the reaction of the chemicals to give a gradual set.

The calcium chloride causes further swelling narcose i-l of the material and thus more eective sealing power. It also heats the solution, thus lowering the viscosity and gives the solution more penetrating power. Most important, however, the moisture out of themud and retains it to be utilized in the setting of the cement in the mixture, thus allowing the material to not dry out too rapidly and thereby cause large cracks ordinarily experienced in the dehydration or muds- The calcium oxide (unslakedlime) gives oi considerable heat and thus lowers the viscosity of the mixture, forming a calcium hydrate, thus making the iinished mass further impermeable.

Alter a given amount of the composition, say seven (7) tons, has been forced through the tubing, under the pressure mentioned, to-wit, 750 to 1,000 pounds per square inch, I clean the tubing by forcing water therethrough. The composition is then allowed toset for a period of 96 to 120 hours, whereupon the tubing may be removed and a suction bailer used for removing the composition within the casing.

In the use of the composition of my invention for the purpose of regaining or re-establishing circulation, where circulation is lost during a rotary drilling operation of the usual type, towi`t, where a sh tail bit is being rotated through the medium of the usuel drill pipe and rotary mud forced downwardly through the drill pipe, out the iish tail, and back between the well hole and the periphery of the drill pipe, the mud may deviate or be lost in water sands. In fact, it is difficult toregain circulation when it is once lost by ordinary methods now known. However, tion, I have found that the composition, properly used es herein described, will permit circulation to be regained. To do this, I pump my composition downwardly through the drill pipe and into the cavity or sands where circulation is lost. The composition is allowed to stand twenty-fourhours, more or less, which will build up a wall preventing the rotary mud from penetrating .the cavity or sands. Thereafter, drilling may be continued as usual.

I claim:

l. A composition for use in oil weils comprising a colloidal jell of clay of the Frazier Mountain and Mojave types combined with cement, calcium chloride, uuslaked lime, bentonite, litharge and caustic, which upon the addition of free water undergoes'a chemical change and hardens into a water impermeable mass.

2. A water shut-oi composition comprising the following approximate parts by weight: 100 parts of clay of the Frazier Mountain and Mojave types in the form of a colloidal jell, 10.5 parts of cement, 1l parts of calcium chloride, 8 parts of unslaked lime. 8 parts of bentonite, 0.5 part of litharge, and 0.05 part of caustic.

3. A water shut-E sealing composition for wells comprising a colloidal jell oi.' clay-of the Frazier Mountain and -Mojave types combined with cement which upon the addition of free water will undergo a chemical change and set ingo ewater impermeable hardened mass. wells comprising a .colloidal Jell of clay of the Frazier Moimtain and Mojave types combined withbentonite and cement which upon the addition or free thence @ned `H-. y

water will undergo a chemical it takes in the formation, particularly water shut-oil sealing composition for" and set into a water impermeable hard. Y

5. A water shut-0H sealing composition for wells comprising a colloidal Jell of clay of the Frazier Mountain and Mojave types .combined with bentonite, cement, and a caustic to lower, the surface tension when the composition undergoes a chemical change and sets into a4 water impermeable hardened mass by the action of free water.

6. A water shut-oil. sealing composition for wells comprising a colloidal jell of clay'of the Frazier Mountain and Mojave types combined with bentonite, cement, a caustic to lower the surface tension when the composition is admixed with free water, which composition undergoes a. chemical change and sets into an impermeable hardened mass by the action of Afree water, and

litharge for slowing up the chemicalreactions between the various ingredients lof the composition and the free Water to give delayed-permanent water impermeable set in said iinal composition.

'1. A water. shut-olf sealing composition for wells comprising a clay of the Frazier Mountain and Mojave types and addition agents homogeneously admixed therewith to form with water a highly colloidal plastic Jell having a speciiic gravity lying between 1.635 and 1.955. and a weight in pounds-per cubic foot lying be vtween 102 and 122; said addition agents com- Y water bearing strata comprising a colloidal Jell of clay of the Frazier Mountain and Mojave types combined with bentonite, litharge and a cement which with the addition of free water undergoes a chemical change and sets finto a water imu permeable hardened mass.

9. A water shut-oli sealing` composition for water bearing strata comprising a colloidal jell of clay of the Frazier Mountain and Mojave types combined with cement, calcium chloride, una slaked lime, bentonite, litharge and caustic which on the addition of free water undergoes a delayed chemical change and sets into a water imxx permeable' hardened mass.

141A water shut-0E sealing composition for water bearing strata comprising a colloidal joli of clay of the Frazier Mountain and Mojave types combined with cement and calcium chloride which upon the addition oi free water undergoes a chemical change and sets into a water impermeable hardened mass.

11. A water shut-od sealing composition for waterbearingstrata comprising a colloidal Jell of clay of the Frazier Mountain and Mojave Icombined with cement and unslaked lime which Aupon the addition of free water undergoes a chemical change and'sets 'into a water imc able hardened mass. 

